This invention relates to protective coatings on decorative compositions and, more specifically, for formulas that facilitate the application thereof. For convenience, the words "clear coating(s)" will be frequently used herein as a generic term for components that are essentially water-white. This invention is particularly concerned with colorants that may temporarily impart color to these otherwise clear coatings, the color dissipating over a relatively short period of time. A further aspect of the invention is a method of designing the concentration of colorant such that the opacity is minimal, thus making it possible to utilize the translucent feature to judge the film thickness.
The function of a clear coating is that, when uniformly applied, it improves the service life and protection afforded by the coating system. Modern high performance coatings are often chosen based upon their ability to maintain their color and gloss over long periods. It has been an aim of manufacturers to achieve more permanency and fastness of color to resist fading for as long as possible. Clear coatings, especially those that are resistant to UV light deterioration, have been found to be highly effective in providing a means to this goal. Clear coatings can be formulated such that they improve the color stability and gloss retention of a base coat and reduce the tendency of color pigments, associated with these base coats, to fade in sunlight. However, to be effective, they must be applied uniformly.
In the past, applying a clear coat at a uniform film thickness over a previously coated surface, especially one that has a high gloss, has been a problem. The applicator has difficulty with the control of the uniformity of wet film thickness since it is difficult to observe the amount of coating that has been applied. Such a limitation is a serious problem, since the amount of protection which the clear coating provides to the underlying base coat (a pigmented coating) is affected by the thickness of the clear coat. If the clear coat is applied at a film thickness that is less than the designed minimum, the resistance to ultra-violet (UV) light transmission through the clear coat is compromised, and the coating's function is compromised. The result is an undesirable variation in color uniformity observed after a period of time.
For the foregoing reasons, there is a need for a paint additive that allows an applicator to judge the thickness of a clear coating film that is being applied to a substrate.